In the kitchen eggs are used in various cooking techniques and processes; and they are as versatile as they are magical, with thickening, absorbing, stabilizing, aerating and lifting capabilities. They also help in clarifying stocks.
In majority of the cases the fresher the eggs the better. Only when eggs are to be whipped should you use older eggs. When eggs are a little older some of their water content has evaporated, leaving the white more viscous, thus more whippable.
Traditionally cooks used to use only yolks as a binding agent, But egg whites too are binding agents as they coagulate- as in quiches, meringues, mousselines, and soufflés. Their flavour is much weaker than that of yolks, however.
About two-thirds of the egg is egg white which is 80% water and 10% protein. The yolk is half water, 15% protein, and 35% fats. Among the fats are lecithin’s which are known as powerful emulsifiers, and cholesterol, which were considered to be harmful to health. Eggs contain a third component-air. A small pocket of air is responsible for the shell breaking when you boil an egg. If you heat up the eggs too rapidly the air has no time to diffuse through the tiny holes in the shell, and the air expansion breaks the shell. On the other hand, this air pocket comes in very useful when you need to check for the freshness of the egg. Put an egg in a large quantity of water: if the volume of the air in the egg is small as in a fresh egg the egg will settle to the bottom of the container. However, if it is not fresh, some water will have evaporated and the air space will be larger and the egg will float.
Egg yolks: Egg yolks are often used as an emulsifier. Many recipes call for the intimate mixing of watery ingredients with oily or fatty ingredients. As a rule, oil and water do not mix, and the oil just floats back to the surface. However, yolks contain a compound called lecithin, which acts a bit like soap, enabling water and oil to mix. These emulsifiers tend to be large particles, parts of which are attracted to water and the other parts being attracted to oil.
One theory is that the oil loving parts embed themselves into the oil droplets, leaving their water loving part sticking out. The sticking out prevents the oil droplets from coming close and joining together. With sauces like Mayonnaise, you first start by adding very little oil to the yolk and vinegar mixture. At first, the amount of emulsifier should be more than the oil, so that it can rapidly and completely coat the oil droplets and make a stable emulsion. Soon you can add more oil as the well-dispersed tiny droplets present can easily break up the larger droplets as you beat.
Egg Whites and Foam:
Foams made from egg whites are very popular especially for creating dishes with a light and delicate texture. The proteins in the egg white are normally tiny little balls, and when you beat they unwrap, elongate and form a web like structure. If you add a little acid like cream of tartar or lemon juice to reduce the alkalinity of the egg white, it will make the foam more stable and less prone to draining.
PARTS OF THE EGG
An egg is made up of albumen, or egg white; the yolk or yellow; and a porous shell. In a cross section, you would find two ropes of Chalazae hold the yolk in the center of the egg. Chalaza is the thick white and in a fresh egg you will find more of it than the thin white. In a fresh egg the air space will be very small.
You will see off centre yolks in hard-boiled eggs that have lost their quality. Also notice the thick white and the thin white when you poach the egg.
The colour of the egg has no relation to the quality of the egg . The color will only indicate the breed of the hen.